The proposed experiments are designed to investigate the learning ability of the fetus in utero. While many questions remain to be answered and should be asked if we are to characterize prenatal influences on postnatal behaviors, methodological problems and ethical considerations make study of the human fetus impossible. Therefore, comparative study is necessitated. Techniques are now available to manipulate the uterine environment making possible the presentation of stimuli to the fetus. The basic procedure is to expose the rat fetus in utero to a conditional stimulus (CS) - a taste/odor stimulus by injecting it into the amniotic fluid. Following this exposure the fetus is injected (intraperitoneal injection) with lithium choloride (LiCl) the aversive unconditioned stimulus (US). Conditioned rats are tested as pups on postnatal day 16 in a nipple preference paradigm or as adults in a two-bottle-preference drinking test. The series of experiments will examine (1) the earliest possible prenatal age at which in utero conditioning is possible; (2) the degree to which the characteristics of the CS and US effect conditioning; and (3) the adult consequences of such prenatal exposures. The proposed experiments are designed to determine the degree to which prenatal experiences can dictate postnatal behaviors.